There has been considerable interest in developing methods for preparing monodisperse polymer particles, i.e., having a narrow particle size distribution, particularly with particle sizes greater than about 2 microns. One polymer of particular interest in this application is polystyrene.
As disclosed in U.S. Pat. No. 4,247,434, which is incorporated herein by reference, microparticles in latex form find utility in a number of applications and yet other applications are awaiting the development of monodisperse polymer particles having a particle size greater than 2 microns. Such polymer particles are used as a reference standard for the calibration of various instruments, in medical research and in medical diagnostic tests.
The difficulty of preparing monodisperse polymer particles is evident from U.S Pat. No. 4,247,434 in which the polymerization is conducted in microgravity, such as in outer-space.
In accordance with this invention the ability to prepare polymer particles in a narrow particle size distribution is enhanced by the use of a more viscous medium during anionic dispersion polymerization.